Sanofi has announced an agreement to acquire Blueprint Medicines Corporation, a US-based biopharmaceutical company specializing in systemic mastocytosis (SM) and other KIT-driven diseases. This acquisition is set to expand Sanofi’s portfolio in rare immunological diseases and add an early-stage pipeline in immunology.
The acquisition includes Ayvakit/Ayvakyt (avapritinib), a medicine approved in the US and the EU for advanced and indolent systemic mastocytosis (ASM & ISM). Ayvakit/Ayvakyt is currently the only approved medicine for this rare immunology disease, which is characterized by the accumulation and activation of aberrant mast cells in various organs. In 2024, Ayvakit achieved net revenues of $479 million, with nearly $150 million in Q1 2025, demonstrating over 60 percent year-on-year growth compared to Q1 2024.
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Beyond Ayvakit/Ayvakyt, the acquisition also brings elenestinib, a next-generation medicine for SM, and BLU-808, a highly selective oral wild-type KIT inhibitor with potential applications across a broad range of immunological diseases. Elenestinib is an oral investigational ISM medication currently undergoing a phase 2/3 study (HARBOR, NCT04910685). BLU-808, an investigational oral, highly potent, and selective wild-type KIT inhibitor, was developed leveraging Blueprint’s expertise in mast cell biology, with wild-type KIT playing a central role in mast cell activation implicated in inflammatory diseases.
Blueprint’s existing presence among allergists, dermatologists, and immunologists is expected to further enhance Sanofi’s growing immunology pipeline.
Under the terms of the agreement, Sanofi will pay $129.00 per share in cash, totaling an equity value of approximately $9.1 billion. Blueprint shareholders will also receive one non-tradeable contingent value right (CVR) per share, entitling them to two potential milestone payments of $2 and $4 per CVR, contingent on future development and regulatory milestones for BLU-808. The total equity value, including potential CVR payments, is approximately $9.5 billion on a fully diluted basis. The upfront offer price represents a premium of approximately 27% over Blueprint’s closing price on May 30, 2025, and about a 34% premium over its 30-trading day volume-weighted average price (VWAP) as of the same date. Including the CVR, the premium is approximately 33% over the closing price and about 40% over the 30-trading day VWAP as of May 30, 2025.
Paul Hudson, CEO of Sanofi, stated, “The proposed acquisition of Blueprint Medicines represents a strategic step forward in our rare and immunology portfolios. It enhances our pipeline and accelerates our transformation into the world’s leading immunology company. This acquisition is fully aligned with our strategic intent to strengthen our existing therapeutic areas, to bring relevant and differentiated medicines to patients and to secure attractive returns to our shareholders. It complements recent acquisitions of early-stage medicines that remain our main field of interest. Sanofi still retains a sizeable capacity for further acquisitions. We are excited to welcome Blueprint’s talented people and we look forward to chasing the miracles of science together. This makes sense for science, for both companies, for healthcare professionals, and – most of all, for patients.”
Kate Haviland, CEO of Blueprint Medicines, commented, “Since our founding, Blueprint Medicines has worked at the intersection of scientific innovation and operational excellence. I’m incredibly proud of the medical innovations our people have created and delivered to patients. We have translated our unique scientific understanding of mast cell biology into a portfolio of important therapies including Ayvakit – the first and only medicine approved to treat the root cause of systemic mastocytosis – and worked collaboratively with communities to improve standards of care and patient outcomes. With this agreement, we begin our next chapter with Sanofi, whose exceptional leadership in rare disease and immunology and proven ability to solve medical challenges at scale stand to accelerate our joint mission to bring life-changing medicines to many more patients around the world.”
Systemic mastocytosis is a rare immunologic disorder caused by the accumulation and activation of aberrant mast cells, leading to debilitating symptoms across multiple organ systems and a significant impact on quality of life. Symptoms can include anaphylaxis, bone disease, gastrointestinal distress, and skin lesions. Indolent systemic mastocytosis (ISM) accounts for the majority of SM cases.
Sanofi plans to finance the transaction using a combination of cash on hand and proceeds from new debt. The tender offer is not subject to any financing conditions. Subject to customary closing conditions and regulatory approvals, Sanofi anticipates completing the acquisition in the third quarter of 2025. The acquisition is not expected to significantly impact Sanofi’s financial guidance for 2025, but it is immediately accretive to gross margin and will be accretive to business operating income and EPS after 2026.
